<template>
  <div class="spec-preview">
    <img :src="skuImageList[defaultIndex]?.imgUrl" />
    <div class="event" @mousemove="mousemove"></div>
    <div class="big">
      <img :src="skuImageList[defaultIndex]?.imgUrl" ref="bigImgEle" />
    </div>
    <div class="mask" ref="maskEle"></div>
  </div>
</template>

<script>
  export default {
  name: "Zoom",
  props: ["skuImageList"],
  mounted() {
    this.$bus.$on("getZoomIndex", (index) => {
      this.defaultIndex = index;
    });
  },
  data() {
    return {
      defaultIndex: 0,
    };
  },
  methods: {
    mousemove(e) {
      //得到鼠标到外层元素边缘的距离
      const mouseToOut = {
        left: e.offsetX,
        top: e.offsetY,
      };

      //计算蒙版的位置
      const maskLoaction = {
        x: mouseToOut.left - this.$refs.maskEle.offsetWidth / 2,
        y: mouseToOut.top - this.$refs.maskEle.offsetHeight / 2,
      };

      //处理临界值
      if (maskLoaction.x < 0) {
        maskLoaction.x = 0;
      } else if (
        maskLoaction.x >=
        e.target.clientWidth - this.$refs.maskEle.offsetWidth
      ) {
        maskLoaction.x = e.target.clientWidth - this.$refs.maskEle.offsetWidth;
      }

      if (maskLoaction.y < 0) {
        maskLoaction.y = 0;
      } else if (
        maskLoaction.y >=
        e.target.clientHeight - this.$refs.maskEle.offsetHeight
      ) {
        maskLoaction.y =
          e.target.clientHeight - this.$refs.maskEle.offsetHeight;
      }

      // 赋值
      this.$refs.maskEle.style.top = maskLoaction.y + "px";
      this.$refs.maskEle.style.left = maskLoaction.x + "px";

      // 控制大图位移
      // 因为想让它向左移动，所以要-2
       this.$refs.bigImgEle.style.left = -2 * maskLoaction.x + "px";
      this.$refs.bigImgEle.style.top = -2 * maskLoaction.y + "px";
      },
    },
  };
</script>

<style lang="less">
  .spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
      width: 100%;
      height: 100%;
    }

    .event {
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0;
      left: 0;
      z-index: 998;
    }

    .mask {
      width: 50%;
      height: 50%;
      background-color: rgba(0, 255, 0, 0.3);
      position: absolute;
      left: 0;
      top: 0;
      display: none;
    }

    .big {
      width: 100%;
      height: 100%;
      position: absolute;
      top: -1px;
      left: 100%;
      border: 1px solid #aaa;
      overflow: hidden;
      z-index: 998;
      display: none;
      background: white;

      img {
        width: 200%;
        max-width: 200%;
        height: 200%;
        position: absolute;
        left: 0;
        top: 0;
      }
    }

    .event:hover~.mask,
    .event:hover~.big {
      display: block;
    }
  }
</style>